Marshall was born Garry Kent Masciarelli in The Bronx, New York on November 13, 1934,[3][4] the son of Anthony Wallace Marshall (1906–99), a director of industrial films and later a producer, and Marjorie Irene (née Ward; 1908-1983), a tap dance teacher who ran a tap dance school.[5] He was the brother of actress/director Penny Marshall and Ronny Marshall Hallin, a television producer. His father was of Italian descent, his family having come from San Martino sulla Marrucina, Chieti, Abruzzo,[6] and his mother was of German, English, and Scottish ancestry.[7] His father changed his last name from Masciarelli to Marshall before Garry was born.[8] Marshall was baptized Presbyterian and also raised Lutheran for a time.[9]

In the early 1980s, he met Hector Elizondo while playing basketball and became great friends. Elizondo appeared in every film that Marshall directed, beginning with his first feature film Young Doctors in Love. Elizondo once noted that he is written into all of Marshall's contracts whether he wanted to do the film or not.[15] In the opening credits of Exit to Eden (their eighth film together), Elizondo is credited "As Usual ... Hector Elizondo".[16] In 1984, Marshall had a film hit as the writer and director of The Flamingo Kid.[17]

A consummate producer, Marshall wore many hats during this period of his career: Most of his hit television series were created and executive produced by him. His first producing assignment came with Hey, Landlord in 1966. He stepped up the very next year, producing The Lucy Show.[18] Then came successes in producing The Odd Couple, Laverne and Shirley, Blansky's Beauties, Mork & Mindy, Angie, and Happy Days. Marshall also launched independent productions through his theater (The Falcon in Toluca Lake) and in association with productions launched with talent he was grooming and working with for years. One such project titled Four Stars was directed by Lynda Goodfriend (who portrayed Lori Beth in Happy Days), and was based on a play Goodfriend had read when she was studying at the Lee Strasberg Center, which had been written by John Schulte and Kevin Mahoney.[19] It starred Julie Paris (the daughter of Jerry Paris) and Bert Kramer. Schulte later co-wrote with TV veteran writer and producer, Fred Fox, Jr., who penned and produced a number of Marshall's television series, including Happy Days and Laverne and Shirley. [20] Marshall went on to focus on directing feature films, with a series of hits, such as Beaches, Pretty Woman, The Princess Diaries, Valentine's Day, and New Year's Eve.[19]

In 1996, Marshall was awarded the Women in FilmLucy Award in recognition of excellence and innovation in creative works that have enhanced the perception of women through the medium of television.[29] He was inducted into the Television Hall of Fame for his contributions to the field of television in 1997.[30]